High specific capacitance solid state supercapacitor and method of manufacture

ABSTRACT

A novel electrode and associated method of manufacturing said novel electrode comprising a porous structure having absorbed polystyrene sulfonate (PSS), a self-assembled polypyrole (PPy) layer adjacent to the PSS absorbed porous structure, a self-assembled polyaniline (PANI) layer adjacent to the PPy layer, an electrochemically deposited PANI layer adjacent to the PPy layer and an electrochemically deposited PANI-molybdenum disulfide (PANI-MoS2) layer adjacent to the electrochemically deposited PANI layer. A supercapacitor and associated method of manufacturing a supercapacitor comprising a first novel electrode and a second novel electrode separated by a polyvinyl gel and a porous separator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentSer. No. 16/839,161, filed Apr. 3, 2020 and entitled “High SpecificCapacitance Solid State Supercapacitor and Method of Manufacture,” whichclaims priority to PCT International Application No. PCT/US2018/054112,filed Oct. 3, 2018 and entitled “High Specific Capacitance Solid StateSupercapacitor and Method of Manufacture,” which claims priority to U.S.Provisional Patent Application No. 62/567,425, filed Oct. 3, 2017 andentitled “High Specific Capacitance in Solid State Supercapacitor,” allof which are herein incorporated by reference in entirety.

BACKGROUND OF INVENTION

Supercapacitors have been one of the emerging energy storagetechnologies with potential applications in small electronics, hybridvehicles, solar and wind farms. The key factors in a supercapacitor arespecific capacitance, specific power, and specific energy which are alllargely dependent upon the nature of electrode materials. To obtain highperformance in a supercapacitor, the electrodes of the device have to beporous with high surface to volume ratio and high conductivity. Also,for employing the pseudocapacitive effect for enhancing a devicecapacitance, the electrode material should present an excellentelectrochemical redox stability at a wide potential window. Highspecific capacitances have been reported in devices made ofnanocomposites of a conducting polymer with graphene, MoS₂, and carbonnanotubes.

A practical method to enhance the porosity of the electrodes is to coatthe composite materials on the surface of a cellulose or spongestructure, such as a solid-state supercapacitor fabricated with largesurface area based carbon nanotubes on bacterial nanocellulose inpoly(styrene-block-ethylene oxide-block-styrene) based ionic liquidelectrolyte. The electrodes based on carbon nanotubes on bacterialnanocellulose had a specific capacitance of (50 F g⁻¹). Porous nitrogendoped carbon fibers showed a specific capacitance of 202 F g⁻¹. Avolumetric capacitance of 2.5 F cm⁻³ in a solid-state supercapacitorbased on carbon fiber and manganese oxide core-shell fiber electrodehave also been demonstrated. Graphene meso and microporousaerogels-based supercapacitor showed a specific capacitance of 325 F g⁻¹in a sulfuric-based electrolyte. A supercapacitor fabricated on a 3Dsponge like nano-structure coated with functionalized multi-walledcarbon nanotubes had an energy density of 7.1 Wh kg⁻¹ and a powerdensity of 48 kW kg⁻¹ in an ionic liquid-based electrolyte. A powerdensity of 63 kW kg⁻¹ and energy density of 31 Wh kg⁻¹ with a manganeseoxide and carbon nanotube sponge-based supercapacitor has also beenreported. It is also known to fabricate supercapacitors by coatinggraphene oxide on polyurethane based sponge, resulting in an energydensity of 89 W h kg⁻¹.

The common approach with aerogel or sponge-based substrates is to dipthe substrate in a conductive ink or to mechanically press a conductivepowder (e.g. carbon nanotubes or graphene) to the substrate to makeconductive porous electrodes. Despite the simplicity of the process, theelectrode conductivity may differ in various parts of the substrate,thereby negatively influencing the properties of a supercapacitor madeby such a process.

Accordingly, what is needed in the art is an improved solid-statesupercapacitor and associated method for manufacturing a solid-statesupercapacitor.

SUMMARY OF THE INVENTION

In various embodiments, the present invention provides an improvedsupercapacitor comprising a common sponge which provides a large surfacearea upon which to fabricate a solid-state supercapacitor. Thesupercapacitor includes two substantially symmetric electrodes separatedby a polyvinyl (PVA) layer. The two electrodes are provided bydepositing conducting polypyrrole (PPy) and polyaniline (PANI) on thesurface of sponge using in-situ self-assembled polymerization technique,wherein the PPY and PANI layers establish conductivity within thesponge. Subsequently, electrochemical PANI and molybdenum disulfide(MoS₂)-PANI are deposited by electrochemical techniques to form theelectrodes. The polyvinyl alcohol (PVA) gel is then synthesized andfurther, polyaniline, polyaniline-graphene and polypyrrole, polypyrrolegraphene are polymerized in PVA gel to obtain highly conductingelectrolyte to fabricate the solid-state supercapacitor.

In one embodiment, an electrode of the present invention includes, aporous structure having absorbed polystyrene sulfonate (PSS), aself-assembled polypyrole (PPy) layer adjacent to the PSS absorbedporous structure, a self-assembled polyaniline (PANI) layer adjacent tothe PPy layer. The electrode may further include, an electrochemicallydeposited PANI layer adjacent to the PPy layer and an electrochemicallydeposited PANI-molybdenum disulfide (PANI-MoS₂) layer adjacent to theelectrochemically deposited PANI layer.

The porous structure may be selected from a sponge, an organic sponge,open-cell polyurethane form polystyrene, wood, foam, honeycomb ceramics,coral, pumice, porous ceramics and aerogel.

Additionally, the PANI layers may include one or more of,PANI-dichalcogenide, polyaniline derivatives (poly-toluidine,poly(ortho-anisidine), poly(methyl aniline), poly(ortho-ethoxyaniline)and its derivatives, polythiophene ‘PTh’, polyethylenedioxythiophene(PEDOT), polyhexylthiophene (PHTh), conducting methyl substitutedpolyaniline, conducting polymer copolymer (poly(aniline-pyrrole)conducting polymer nanocomposite films with graphene (G), carbonnanotubes tin oxide, titanium oxide (TiO₂), tungsten oxide (WO₃),nanodiamond, zinc oxide over polyaniline film.

In another embodiment, the present invention provides a supercapacitorincluding a first electrode and a second electrode separated bypolyvinyl alcohol (PVA) layer and a separator. The first electrode andthe second electrode including a porous structure having absorbedpolystyrene sulfonate (PSS), a self-assembled polypyrole (PPy) layeradjacent to the PSS absorbed porous structure, a self-assembledpolyaniline (PANI) layer adjacent to the PPy layer, an electrochemicallydeposited PANI layer adjacent to the PPy layer and an electrochemicallydeposited PANI-molybdenum disulfide (PANT-MoS₂) layer adjacent to theelectrochemically deposited PANI layer.

The supercapacitor may further include a graphite sheet/copper tapelayer adjacent to the PSS porous structure of the first electrode andthe second electrode.

In another embodiment, the present invention provides a method formanufacturing an electrode which includes, contacting a porous structurewith a polyanion solution of polystyrene sulfonate (PSS) to form aporous structure/PSS substrate, performing in-situ self-assemblypolymerization of pyrrole (PPy) on the porous structure/PSS substrate toform a porous structure/PSS/PPy substrate, performing in-situself-assembly polymerization of polyaniline (PANI) on the porousstructure/PSS/PPy substrate to form a porous structure/PSS/PPy/PANIsubstrate. The method may further include, electrochemically depositinga layer of PANI on the porous structure/PSS/PPy/PANI substrate to form aporous structure/PSS/PPy/PANI/PANI substrate and electrochemicallydepositing a polyaniline molybdenum disulfide (PANI-MoS₂) layer over theporous structure/PSS/PPy/PANI/PANI substrate to form a porousstructure/PSS/PPy/PANI/PANI/PANI-MoS₂ electrode.

A method for manufacturing a supercapacitor is additionally providedwhich includes, manufacturing a first electrode and a second electrodeby the process including, contacting a porous structure with a polyanionsolution of polystyrene sulfonate (PSS) to form a porous structure/PSSsubstrate, performing in-situ self-assembly polymerization of pyrrole(PPy) on the porous structure/PSS substrate to form a porousstructure/PSS/PPy substrate, performing in-situ self-assemblypolymerization of polyaniline (PANI) on the porous structure/PSS/PPysubstrate to form a porous structure/PSS/PPy/PANI substrate,electrochemically depositing a layer of PANI on the porousstructure/PSS/PPy/PANI substrate to form a porousstructure/PSS/PPy/PANI/PANI substrate and electrochemically depositing apolyaniline molybdenum disulfide (PANI-MoS₂) layer over the porousstructure/PSS/PPy/PANI/PANI substrate to form a porousstructure/PSS/PPy/PANI/PANI/PANI-MoS₂ electrode. The method furtherincludes, applying a first polyvinyl (PVA) gel layer to the PANI-MoS₂layer of the porous structure/PSS/PPY/PANI/PANI/PANI-MoS₂ firstelectrode, positioning a separator on the PVA gel layer, applying asecond PVA gel layer between the separator and the PANI-MoS₂ layer ofthe porous structure/PSS/PPY/PANI/PANI/PANI-MoS₂ second electrode,positioning a first graphite sheet covered with copper tape on anexterior side of the first electrode and positioning a second graphitesheet covered with copper tape on an exterior side of the secondelectrode to form the supercapacitor.

In a particular embodiment, the supercapacitor can be a large surfacearea based sponge/polystyrene sulfonate (PSS)/polypyrrole(PPY)/polyaniline (PANI)/PANI-molybdenum disulfide (MoS₂)-poly(vinylalcohol) (PVA)-PANT-MoS₂/PANI/PPY/PSS Sponge based solid statesupercapacitor.

In an additional embodiment, the supercapacitor can be large surfacearea based sponge/polystyrene sulfonate (PSS)/polypyrrole(PPY)/polyaniline (PANI)/PANI-molybdenum disulfide (MoS₂)-(PVA-gel &graphene) polymerized with PANI-poly(vinyl alcohol)(PVA)-gel-PANI-MoS₂/PANI/PPY/PSSSponge based solid state supercapacitor.

In another embodiment, the supercapacitor can be a large surface areabased sponge/polystyrene sulfonate (PSS)/polypyrrole (PPY)/polyaniline(PANI)/PANI-molybdenum disulfide (MoS₂)-(PVA-gel & graphene) polymerizedwith PPY-PANI-MoS₂/PANI/PPY/PSS/sponge containing based electrolyte andassembly of solid state supercapacitor.

In a particular embodiment, the poly(vinyl alcohol) (PVA) gel may besynthesized in acid. The PVA-gel may be mixed with aniline monomer,graphene and later, added with solution containing ammoniumperdisulphate dissolved in 1 M HCl. The aniline may be polymerized overPVA-gel and graphene and results tino a gel of PVA-PANI-graphene.Similarly, PVA-PPY-graphene, PVA-polythiophene-graphene, gel can beprepared. The gel can be prepared from one or mixtures of polyvinylalcohol, poly (vinyl acetate, poly (vinyl alcohol co-vinyl acetate),poly (methyl methacrylate, poly (vinyl alcohol-co-ethylene ethylene),poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate), polyvinylbutyral, polyvinyl chloride, polystyrene. The combination of eachpolymer at different proportions can also be used for fabrication ofPVA-gel used for making supercapacitor. The gel mixed polyaniline,polyaniline-graphene and polypyrrole, polypyrrole graphene may bepolymerized in PVA gel to obtain highly conducting electrolyte tofabricate the solid state supercapacitor.

In a specific embodiment, wherein the porous structure is a sponge, theelectrode can be fabricated for such structures assponge/PSS/PPY/PANI/PPY-MoS₂, sponge/PSS/PPY/PPY/PANI-MoS₂,sponge/PSS/PPY/PPY/polythiophene-MoS₂, sponge/PSS/PPY/PPY/poly(o-anisidine)-MoS₂, sponge/PSS/PPY/PPY/poly(o-toluidine)-MoS₂,sponge/PSS/PPY/PPY/PPY-MoS₂,sponge/PSS/PPY/PPY/poly(o-ethoxyaniline)-MoS₂,sponge/PSS/PPY/PPY/substituted-MoS₂, sponge/PSS/PPY/PPY/PPY-PANI-MoS₂,sponge/PSS/PPY/PPY/PPY-MoS₂, sponge/PSS/PPY/PANI/PPY-MoS₂,sponge/PSS/PPY/PANI/substituted PPY-MoS₂, sponge/PSS/PPY/PANI/PPY-WS₂,sponge/PSS/PPY/PANI/substituted PANI-WS₂, sponge/PSS/PPY/PANI/PPY-WS₂,sponge/PSS/PPY/PANI/substituted PPY-graphene,sponge/PSS/PPY/PANI/PPY-graphene, sponge/PSS/PPY/PANI/substitutedPANT-Carbon nanotube (CNTs), sponge/PSS/PPY/PANI/substituted PPY-CNTs,the mixed PPY, PANI and polythiophene or mixture layers can befabricated.

Additionally, sponge/PSS/PPY/PANI/PPY-MoS₂-PVA-gel-MoS₂-PANI/PPYPANI/PPY/PSS/sponge symmetric orsponge/PSS/PPY/PANI/PPY-MoS₂-PVA-gel-MoS₂-PPY/PPY/PSS/spongesupercapacitor may be formed. The combinations can be made from the gelmixtures described above. The PVA-gel consisting of polyaniline andgraphene can also be used as electrolyte.

Accordingly, in various embodiments the present invention provides forimproved electrodes and associated supercapacitors formed from saidinventive electrodes, thereby providing a device exhibiting improvedcapacitance over other structures known in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference should be made tothe following detailed description, taken in connection with theaccompanying drawings, in which:

FIG. 1 is a series of images depicting the steps of electrodefabrication in which PPY, PANI and PANI-MoS₂ are deposited over sponge,in accordance with an embodiment of the present invention.

FIG. 2 is an image depicting the formation of a PVA based gelelectrolyte, in accordance with an embodiment of the present invention.

FIG. 3 is a series of images depicting the fabrication steps of asponge-based solid supercapacitor, in accordance with an embodiment ofthe present invention.

FIG. 4 is a schematic of the sponge-based supercapacitor using coppertape/graphite sheet/sponge/PSS/PPY/PANI/PANI/PANI-MoS₂/PVAgel/sponge/PSS/PPY/PANI/PANI/PANI-MoS₂/graphite sheet/copper sheet, inaccordance with an embodiment of the present invention.

FIG. 5A is an SEM image of a pure sponge, in accordance with anembodiment of the present invention.

FIG. 5B is a magnified image of the SEM image of the pure sponge of FIG.5A, in accordance with an embodiment of the present invention.

FIG. 5C is an SEM image of a pure sponge/PPy, in accordance with anembodiment of the present invention.

FIG. 5D is a magnified image of the SEM image of the pure sponge/PPysubstrate of FIG. 5C, in accordance with an embodiment of the presentinvention.

FIG. 5E is an SEM image of a pure sponge/PPy/PANI substrate (via in-situself-assembly), in accordance with an embodiment of the presentinvention.

FIG. 5F is a magnified image of the SEM image of the puresponge/PPy/PANI substrate of FIG. 5E, in accordance with an embodimentof the present invention.

FIG. 5G is an SEM image of a pure sponge/PPy/PANI/PANI-MoS₂ substrate(via electrochemical deposition), in accordance with an embodiment ofthe present invention.

FIG. 5H is a magnified image of the SEM image of the puresponge/PPy/PANI/PANI-MoS₂ substrate of FIG. 5G, in accordance with anembodiment of the present invention.

FIG. 6A is a graphical illustration of the X-ray diffraction ofPPY/PANI/MoS₂, in accordance with an embodiment of the presentinvention.

FIG. 6B is a graphical illustration of the FTIR spectra of PPY, PPY/PANIand PPY/PANI/MoS₂ deposited on sponges from 600-2000 cm⁻¹, in accordancewith an embodiment of the present invention.

FIG. 7A is a graphical illustration of the CV as a function of scanrates at (1) 5 mV/s (2) 10 mV/s (3) 20 mV/s (4) 50 mV/s and (5) 100mV/s, in accordance with an embodiment of the supercapacitor of thepresent invention.

FIG. 7B is a graphical illustration of the CV of the supercapacitor at10 mV/s, in accordance with an embodiment of the present invention.

FIG. 7C is a graphical illustration of the specific capacitance of thesupercapacitor, estimated using CV studies, in accordance with anembodiment of the present invention.

FIG. 7D is a graphical illustration of the charge/discharge cyclingperformance of the supercapacitor at 30 mA, in accordance with anembodiment of the present invention.

FIG. 8 is a graphical image depicting CV cycling performance at 20 mV/sfor 1000 cycles (inset) CV curves collected at the 1^(st) and the1000^(th) cycle, in accordance with an embodiment of the supercapacitorof the present invention.

FIG. 9 is a graph depicting leakage current when charging with constantvoltage of 1V over a duration of 500 seconds, in accordance with anembodiment of the supercapacitor of the present invention.

FIG. 10A is a graphical image depicting CVs curves as a function of scanrate 5, 10, 20, 50 and 100 mV/sec of 2 years old symmetricsupercapacitor based on sponge/PSS/PPY/PPY/PPY-MoS₂ electrode materials,in accordance with an embodiment of the supercapacitor of the presentinvention.

FIG. 10B is a graphical illustration of and PVA-gel as an electrolytesec (inset) at 10 mV/s, in accordance with an embodiment of thesupercapacitor of the present invention.

FIG. 11 is a graph depicting Nyquist plots (inset) of the appliedequivalent circuit of the sponge supercapacitor, in accordance with anembodiment of the supercapacitor of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings, which form a parthereof, and within which are shown by way of illustration specificembodiments by which the invention may be practiced. It is to beunderstood that other embodiments by which the invention may bepracticed. It is to be understood that other embodiments may beutilized, and structural changes may be made without departing from thescope of the invention.

While organic sponge, polyurethane and foam-based polystyrene basedporous materials are inexpensive, they are also naturally insulating.The present invention transforms a sponge into a nearly metallicconductivity through the deposition of conducting polymer, utilizingboth in-situ and electrochemical techniques. In addition to providingthe substrate, the sponge also contains the hybrid network within itslarge surface area, which enables fabrication of a high specificcapacitance based supercapacitor. As such, in various embodiments,porous materials, such as wood, foam material, honeycomb ceramics,coral, pumice, porous ceramics, open-cell polyurethane foam, aerogel,etc. can be used to make an inexpensive conducting and solid-statesupercapacitor.

In various embodiments, the present invention provides a multilayerstructure electrode built on a sponge substrate and a solid-statesupercapacitor having a polyvinyl alcohol (PVA) gel-based electrolyte,which utilizes the novel electrode. To build the electrode in-situ,self-assembled polymerization of both PPy and PANI were used toestablish a conductive surface for the subsequent electrochemicalpolymerization of molybdenum disulfide (MoS₂)-PANI nanocomposite toobtain the supercapacitor electrodes. The electrochemical study resultsare promising toward practical application of the multilayer electrodestructure for high power and high energy density supercapacitors.

With reference to FIG. 1 , in one embodiment the electrode fabricationsteps 100, utilizing a commercial kitchen sponge are illustrated. Inthis embodiment, the sponge was washed in deionized water and thendipped in a polyanion solution of polystyrene sulfonate (PSS) (2 mg/ml)for 24 hours to form a sponge/PSS substrate 105. In a specificembodiment, the sponge may be a high-density foam. The PSS treatmentallowed the sponge surface to absorb negative charges of anions.

Next, pyrrole (PPy) was polymerized by in-situ self-assemblypolymerization over the PSS treated sponge 105 resulting in asponge/PSS/PPy substrate 110. In a particular embodiment, 0.1M pyrroleand 0.1M para-toluene sulfonic acid were added to a 1M HCl solution,followed by 0.05M iron chloride, which was then stirred for a fewseconds. The sponge/PSS substrate was then dipped in the resultingsolution and held for 3 hours. The sponge/PSS/PPy was then cleaned andkept in 1M HCl solution.

A layer of polyalanine (PANI) was then deposited on the sponge/PSS/PPysubstrate 110 to form a sponge/PSS/PPy/PANI substrate 115. In aparticular embodiment, the PANI was deposited by in-situ self-assembledtechnique using a solution of 0.2M aniline, 0.1M of an oxidizing agent(ammonium persulfate, APS) in 1M HCl for a duration of 3 hours.

The second layer of PANI was then deposited on the sponge/PSS/PPy/PANIsubstrate 115 to form a sponge/PSS/PPy/PANI/PANI substrate 120. In aparticular embodiment, the second layer of PANI was deposited by anelectrochemical technique in 0.2 aniline in 1 M HCl at a potential of1.5 V for a duration of 2 hours, for each side of the sponge.

The final layer of PANI-MoS₂ was then electrochemically deposited overthe sponge/PSS/PPy/PANI substrate 120 to form a sponge/PSS/PPy/PANI-MoS₂substrate 125. In a particular embodiment the PANI-MoS₂ was deposited inan electrochemical cell at 1.5 V in a solution containing 0.2 M aniline,0.5 g MoS₂, 1 g cetrimonium bromide ‘CTAB’ for a duration of 2 hours.The sponge/PSS/PPy/PANI-MoS₂ substrate was made upside down, and furtherdeposition was also made at 1.5 V for an additional 2 hours to completethe deposition process. These processing steps resulted in a nearlymetallic conductivity in the sponge/PSS/PPy/PANI/PANI-MoS₂ layers.

FIG. 1 illustrates the steps 100 involved in the electrode fabricationprocess of the present invention and the chemical structures of theconducting polymer and its composite materials. Following thefabrication steps, the sponge/PSS/PPy/PANI-MoS₂ was cleaned usingdeionized water, and subsequently in 1 M HCl, and gently squeezed toremove the acid and left to dry at room temperature for 24 hours. Thesponge/PSS/PPy/PANI/PANI-MoS₂ electrode was subsequently used tocharacterize and fabricate a solid supercapacitor.

For the preparation of the PVA-gel employed in the solid supercapacitor,10 g of poly(vinyl alcohol) (PVA) was added to 100 ml of 1M HCl, whichwas then stirred, under heat at 80C° for a duration 24 hours. The gelwas then allowed to age for one week prior to the fabrication of thesupercapacitor. FIG. 2 illustrates the structure 200 of the PVA-gel.

FIG. 3 illustrates the methods steps 300 in the fabrication of thesponge-based solid supercapacitor of the present invention. In a firststep 305 for the preparation of the supercapacitor, thesponge/PSS/PPy/PANI/PANI-MoS₂ was used for both electrodes 310, 315 inthe symmetric supercapacitor structure. The PVA gel electrolyte 320 wasapplied to the electrodes 310, 315 and a porous filter paper that wasused as the separator 330. The electrodes 310, 315, PVA gel 320 andseparator 330 were sandwiches together in a second step 340. In a thirdstep 350, a copper tape 365, 370 was used as the current collector foreach electrode 310, 315. The completed device 360 was assembled bysandwiching two electrodes 310, 315 and the separator 330 between twolayers of plexiglass and tightened with four screws.

FIG. 4 illustrates the various layers of the sponge-based solidsupercapacitor 400. In this embodiment the supercapacitor 400 includes,in order from top to bottom, a first copper tape layer 405 over a firstgraphite sheet 410, a first sponge/PSS/PPy/PANI/PANI-MoS₂ electrode 415,a first PVA gel layer 425 a separator 435, a second PVA gel layer 430, asecond sponge/PSS/PPy/PANI/PANI-MoS₂ electrode 420, a second graphitesheet 450 and a second copper tape layer 440.

To analyze the physical and structural characteristics of the solidsupercapacitor, field emission scanning electron microscopy (FE-SEM,SU70, at accelerating voltage of 5 kV) was used to image the sponge andeach deposited conducting polymer, in addition to the compositestructure on the sponge. FIG. 5A and FIG. 5B illustrate an SEM image ofthe pure sponge. FIG. 5C and FIG. 5D present images of the sponge/PPylayer. FIG. 5E and FIG. 5F present images of the sponge/PPy/PANI (viain-situ self-assembly) layer. FIG. 5G and FIG. 5H present images of thesponge/PPy/PANI/PANI-MoS₂ (via electrochemical deposition) layer. Thestructure of the sponge before and after the PPy layer is different, asshown in FIG. 5C and FIG. 5D. The smaller magnification shows equallydistributed PPy particles approximately 1000 nm to 3500 nm in size.Further, the PANI deposition over PPy changed the structure, wherebynanostructures are clearly visible over the sponge surface as shown inFIG. 5E and FIG. 5F. The PANI-MoS₂ is a clearly distinguishablestructure that is different than both PPy and PANI, following theelectrochemical deposition. The MoS₂ platelets are observed in the PANInetwork in the SEM images of FIG. 5G and FIG. 5H.

A Philips Panalytical Xpert Pro MRD with Cu Kα radiation(wavelength=1.5442 Å) and 20 range from 5° to 45° was then used to studythe X-ray diffraction (XRD) of sponge/PSS/PPy/PANI-MoS₂. As shown inFIG. 6A, peaks for diffraction angle ‘20θ’ at 6.8, 11, 14.4, 33.6, 38and 40.7 degrees were found in the results. Generally, the emeraldinesalt of PANI is quasi crystalline and PPY is amorphous in nature.However, the composite with MoS₂ structure is ordered state than theconventional PANI as well as PPy structure.

FTIR spectra of sponge/PSS/PPy, sponge/PSS/PPy/PANI andsponge/PSS/PPy/PANI/PANI-MoS₂ was measured using Perkin Elmerspectrometer from 600-2000 cm⁻¹ in the reflectance mode. In FIG. 6B,curve 1 shows the infrared peaks at 1936, 1824, 1726 ((C═N, C—N)), 1586(C═C stretching), 1494, 1332 (C═N, C—N) bonds, 1242 (N—H plane mode),1114 (C—H in plane mode), 972 (C—H wag), 833 (C-H waging), 749 and 694cm⁻¹ [29]. Curve 2 in FIG. 6B shows the vibrational bands at 1933, 1821,1722, 1595, 1406, 1332, 1233, 1114, 969, 824, 728, 627 cm⁻¹. Curve 3 inFIG. 6B shows the infrared peaks at 1940, 1822, 1729, 1600, 1490, 1394,1338, 1215, 1114, 962, 846, 742, 867, 665 and 643 cm⁻¹. As illustrated,there is a decrease in the wavenumber in IR spectra after PANI waspolymerized over PPy, which could be due to formation of some hydrogenbonds in the doped form of PANI. 663 cm⁻¹ is the characteristic shiftedpeak of MoS₂

To assess the electrochemical characteristics of the sponge-basedsuperconductor device, electrochemical tests, including CV, CCCD andEIS, were conducted using the two-electrode configuration. FIG. 7A showsthe CV curves of the device at different scan rates from 5 mV s⁻¹ to 100mV s⁻¹. Oxidation and reduction peaks are observed at 0.34V and −0.37V,respectively, for the scan rate of 5 mV s⁻¹. The peaks were shifted to0.8 V (oxidation) and −0.74V (reduction) at 100 mV s⁻¹ scan rate.

FIG. 7B shows the CV plot at 10 mV s⁻¹ scan rate to show the redoxpeaks. The visible redox peaks at different scan rates imply the strongcharge storage via the pseudocapacitive effect in addition to the doublelayer effect. The highest specific capacitance of ˜569 F g⁻¹ has beencalculated from the 5 mV s⁻¹ CV result. FIG. 7C shows the charging anddischarging behaviors of the sponge/PSS/PPy/PANI//PANI-MoS₂supercapacitor with the PVA-gel electrolyte. The specific capacitance,specific power density and specific energy density have been calculatedto be 631.6 Fg⁻¹, 475 W kg⁻¹ and 79.17 Wh kg⁻¹ considering the weight ofonly electrode material. In order to test the stability of the device inmultiple cycles, CV results of 1500 cycles were collected when the scanrate was 100 mV s⁻¹. FIG. 7D shows the Nyquist plot ofsponge/PSS/PPy/PANI/PANI-MoS₂ based supercapacitor fabricated usingPVA-gel. There is a direct fitting of the Nyquist plot and the value ofR1, C1, R2 and CPE1 has been estimated 297.7 μF, 2.0817 Ω, 5.180Ω andAw1=3.041, P1=0.05 and n1=0.5889.

FIG. 8 shows a retention of ˜94% CV for cycling performance at 1000 mVs⁻¹ for 1500 cycles (inset) CV curves collected at the 1^(st) and the1000th cycle.

To study the leakage currant in the sponge supercapacitor, a constantpotential of 1 V was applied for 500 seconds. By monitoring the chargingcurrant at the end of charging cycle, it was 4.5 mA which can beencorresponding to the leakage currant in the device as shown in FIG. 9 .FIG. 10A illustrates CVs curves as a function of scan rate 5, 10, 20, 50and 100 mV/sec of symmetric supercapacitor based on 2 years oldsponge/PPy/PANI/PANI-MoS₂ electrode materials and PVA-gel as anelectrolyte. The cyclability of this 2-year-old supercapacitor isexamined under long-term charge/discharge cycling over 100 cycles, whichhas shown a good cyclic performance and reversibility as evidenced byFIG. 10B.

FIG. 11 shows the Nyquist plot of sponge/PPy/PANI/PANI-MoS₂ basedsupercapacitor fabricated using PVA-gel. There is a direct fitting ofthe Nyquist plot and the value of R1, C1, R2 and CPE1 has beenestimated. The C1 297.7 μF, R1 2.0817, R2=5.180, Aw1=3.041, P1=0.05 andn1=0.5889.

As described in detail, in various embodiments, the present inventionprovides a multilayer electrode structure with conducting polymers and acomposite material of molybdenum disulfide (MoS₂) that was designed andfabricated on a kitchen sponge substrate to make solid statesupercapacitors with a high specific capacitance of 631.6 F g⁻¹.

In various embodiments, the sponge-based electrode was fabricated byin-situ self-assembled polymerization of a layer of polypyrrole (PPy)and a layer of polyaniline (PANI) on a sponge substrate. The layers ofPPy and PANI converted the sponge surface to a conductive surface thatwas used for the electrochemical deposition of a thicker layer of PANIand another layer of PANI-MoS₂-PANI composite. The polyvinyl alcohol(PVA) gel was synthesized and further, PANI, was polymerized in PVA gelto obtain highly conducting electrolyte.

The fabrication, characterization and results demonstrate that largesurface area based sponge PSS/PPy//PANI/PANI-MoS₂ electrodes maypotential use as supercapacitor electrode materials for a promisinglow-cost supercapacitor which exhibits good electrochemical performancewith superior cycle durability, time stability and shelf life.

In the preceding specification, all documents, acts, or informationdisclosed does not constitute an admission that the document, act, orinformation of any combination thereof was publicly available, known tothe public, part of the general knowledge in the art, or was known to berelevant to solve any problem at the time of priority.

The disclosures of all publications cited above are expresslyincorporated herein by reference, each in its entirety, to the sameextent as if each were incorporated by reference individually.

It will be seen that the advantages set forth above, and those madeapparent from the foregoing description, are efficiently attained andsince certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatters contained in the foregoing description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall there between. Now that theinvention has been described,

What is claimed is:
 1. An electrode comprising: a porous structurehaving absorbed polystyrene sulfonate (PSS); a self-assembled polypyrole(PPy) layer adjacent to the PSS absorbed porous structure; and aself-assembled polyaniline (PANI) layer adjacent to the PPy layer. 2.The electrode of claim 1, further comprising: an electrochemicallydeposited PANI layer adjacent to the PPy layer, wherein theelectrochemically deposited PANI layer is thicker than theself-assembled PANI layer; and an electrochemically depositedPANI-molybdenum disulfide (PANI-MoS₂) layer adjacent to theelectrochemically deposited PANI layer.
 3. The electrode of claim 1,wherein the porous structure is selected from a sponge, an organicsponge, open-cell polyurethane form polystyrene, wood, foam, honeycombceramics, coral, pumice, porous ceramics and aerogel.
 4. Asupercapacitor comprising: a first electrode comprising; a porousstructure having absorbed polystyrene sulfonate (PSS); a self-assembledpolypyrole (PPy) layer adjacent to the PSS absorbed porous structure; aself-assembled polyaniline (PANI) layer adjacent to the PPy layer; anelectrochemically deposited PANI layer adjacent to the PPy layer; anelectrochemically deposited PANI-molybdenum disulfide (PANI-MoS₂) layeradjacent to the electrochemically deposited PANI layer; a secondelectrode comprising; a porous structure having absorbed polystyrenesulfonate (PSS); a self-assembled polypyrole (PPy) layer adjacent to thePSS absorbed porous structure; a self-assembled polyaniline (PANI) layeradjacent to the PPy layer; an electrochemically deposited PANI layeradjacent to the PPy layer; and an electrochemically depositedPANI-molybdenum disulfide (PANI-MoS₂) layer adjacent to theelectrochemically deposited PANI layer.
 5. The supercapacitor of claim4, wherein the porous structure of the first electrode and the secondelectrode is selected from a sponge, an organic sponge, open-cellpolyurethane form polystyrene, wood, foam, honeycomb ceramics, coral,pumice, porous ceramics and aerogel.
 6. The supercapacitor of claim 4,wherein the first electrode and the second electrode further comprises acopper tape layer adjacent to the PSS porous structure.
 7. Thesupercapacitor of claim 6, wherein the first electrode and the secondelectrode further comprises a graphite sheet layer adjacent to thecopper tape layer.
 8. A method for manufacturing an electrode, themethod comprising: contacting a porous structure with a polyanionsolution of polystyrene sulfonate (PSS) to form a porous structure/PSSsubstrate; performing in-situ self-assembly polymerization of pyrrole(PPy) on the porous structure/PSS substrate to form a porousstructure/PSS/PPy substrate; and performing in-situ self-assemblypolymerization of polyaniline (PANI) on the porous structure/PSS/PPysubstrate to form a porous structure/PSS/PPy/PANI substrate.
 9. Themethod of claim 8, wherein the porous structure is selected from asponge, an organic sponge, open-cell polyurethane form polystyrene,wood, foam, honeycomb ceramics, coral, pumice, porous ceramics andaerogel.
 10. A method of manufacturing a supercapacitor, the methodcomprising: manufacturing a first electrode and a second electrode bythe process comprising; contacting a porous structure with a polyanionsolution of polystyrene sulfonate (PSS) to form a porous structure/PSSsubstrate; performing in-situ self-assembly polymerization of pyrrole(PPy) on the porous structure/PSS substrate to form a porousstructure/PSS/PPy substrate; performing in-situ self-assemblypolymerization of polyaniline (PANI) on the porous structure/PSS/PPysubstrate to form a porous structure/PSS/PPy/PANI substrate;electrochemically depositing a layer of PANI on the porous structure/PSS/PPy/PANI substrate to form a porous structure/PSS/PPy/PANI/PANIsubstrate; and electrochemically depositing a polyaniline molybdenumdisulfide (PANI-MoS₂) layer over the porous structure/PSS/PPy/PANI/PANIsubstrate to form a porous structure/PSS/PPy/PANI/PANI/PANI-MoS₂electrode.
 11. The method of claim 10, wherein the porous structure ofthe first electrode and the second electrode is selected from a sponge,an organic sponge, open-cell polyurethane form polystyrene, wood, foam,honeycomb ceramics, coral, pumice, porous ceramics and aerogel.